Start with the known (you) and work back to the unknown (previous generations).
What information is contained on your birth certificate that helps you to find your parents' marriage certificate and birth certificates? When you have viewed those certificates, what information on them helps you to locate the records for the previous generation?
Document thoroughly where you found your information and where you looked. Ensure it is complete so that others can also find the same records if they wish.
Try to obtain birth, marriage and death details on a person (where applicable) before going back to the previous generation. It's not a race to collect as many family members as you can in as short a time as possible. Being methodical and thorough helps to prevent errors and repeating research.
Talk to living family members about their memories. Ideally record this conversation. What clues do they provide about where to look for more information? Be aware that memories are not always correct. Some people genuinely "remember" an event incorrectly. Others have reason to intentionally lie. Try to verify the facts they provide with records, where records may possibly exist. For example, facts like employment or moving to a different town may be verified with other records. These help to establish a timeline that may be necessary for further research. Their regular family activity on a Friday night probably can't be verified, and really doesn't need to be, but there may be a photo and an interesting story to include in a biography.
Learn how records are created, and the pros and cons of each. Generally speaking, those records that were created at the time of the event, or near the time of the event, are likely to be the most accurate, e.g. birth records, marriage records. They are not infallible however. Comparing them to as many different sources as possible will highlight unreliable information that requires further research to resolve.
